A Demonstration of Sample Segregation

Abstract

Handling a solid mixture can segregate its particles by size. A simple, visually-compelling demonstration shows students how stirring or pouring can segregate a mixture and create a nonuniform sample. The demonstration uses colored beads and other inexpensive, readily-available materials. The demonstration has proven useful for illustrating the importance of sample handling for students studying analytical chemistry and environmental chemistry.Find this demonstration and others in the DigiDemos area of the JCE Digital Library.

Chemical Analysis of Household Oxygen-Based Powdered Bleach: An Engaging Approach to Teaching Sampling of Heterogeneous Materials and Addressing Statistics

“…Sampling is a fundamental step in chemical analysis and a determining factor of the representativeness of the result, especially for the analysis of nonhomogeneous target materials. Even though it is a subject treated in most analytical chemistry textbooks, and occasionally in this Journal , − it remains untaught by many universities and colleges, and is seldom practiced in chemistry undergraduate or technical courses. This is likely because there are few published activities well-suited for realistic, practical work during laboratory courses.…”

“…The students are asked to perform a time-consuming gravimetric determination of nickel dimethylglyoximate (in triplicate) . In another example, colored plastic beads are mixed for visual observation of the segregation after stirring or pouring . Experiments with real samples suitable for application in lab classes are, however, rarely presented.…”

“…5 In another example, colored plastic beads are mixed for visual observation of the segregation after stirring or pouring. 8 Experiments with real samples suitable for application in lab classes are, however, rarely presented. The segregated oxygen bleach powder in its original package is perfectly suited for this purpose, as will be shown.…”